Grid structure



W. B. REED GRID STRUCTURE Oct. 26, 1948.

Filed Dec. 29, 1945 FIQI IN-VEIVNTOR WILL/AM Bmoroleo REED Patented Oct. 26, 1948 NITED STATES PATENT OFFICE GRID STRUCTURE William Bradford Reed, Westwood, Mass, as-

signor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application December 29,1945, Serial No, 637,888 e Claims. (Cl. 25027..5')

This invention relates to the structure of thermionic tubes, and more particularly to a novel grid element and structure for use in such tubes.

manner, and bear on the lower surface of spacer 2, as shown. Spacers l and 2 are therebyv positively prevented from movin further away from each The device of the invention finds its most useful oth'er. Firmly supported by the upper end of rod application in the field of very small thermionic 5 4, as by means of conducting spring me er tubes, for example, those of the sub-miniature which is attached to rod 4 at one end and to the type, although it is not to be construed in any way filament at its other end, is an electron-emitting as limited thereto. element I l here shownas a filamentaw-typecath- An object of the invention is to devise a grid ode. Element H passes through spacer l, exstructure which provides a more eiiective control 10 ds b t n Spacers and and its lower over the flow of electrons in the tube than that end passes through spac r e n fi y a obtainable in prior art structures. tached thereto by means of bracket 24. Lead l2 Another object is to devise a grid structure i is attached to the lower end of rod 4 and lead l3 which extremely close spacing of the grid wires is attached to bracket 24. may be obtained. The control grid of the tube is indicated as a Another object is to provide a grid structure Whole at s d element s e by st which is inherently strong and which will mainwinding one group of individual wires helically in tain its initial shape without the necessity of any n direction a u the periphery of a cyli e internal supportin means. using as a cylindrical form a section of relatively A further object is to devise a grid structure rigid Wire, uch s opper Wi e. he lon d in which the conventional grid side-supports are axes of the individual wires are made parallel to completely eliminated, and in which the grid is a other a d a s a d xtr m y l s t supported in position in th t b by novel means, each other, since in the device of this invention Another object is to devise a grid of very small grid wires of extremely small diameter are usedsize which is relatively simple and yet at the A second group of individual wires is then wound same time highly effective. helically in the opposite direction about the pe- Other and further objects and advantages of riphery of the same cylinder, utilizing a similarthe present invention will become apparent, and parallel relation and close spacing of th longithe foregoing will be understood in t o t t tudinal axes of the individual wires. Actually, offollowing 'exemplifications thereof, reference be- 3 course, si ce e above process is carried 01115 On ing had to the accompanying drawing in wh1ch a braiding ac ne, the two groups f Wires are Fig 1 represents, partly in cross-section and wound at substantially the same time. As will, partly in perspective, a fr nt vi of th be evident, due to the fact that the two groups plete tube element assembly; of wires are wound helically in opposite directions Fig. 2 is an enlarged fragmentary view of Fig. about the periphery of the Same Cylinder, the. 1 showing the m an for supporting the grid; wires of each group will cross over those of the Fig. 3 is a cross-section taken on line 3-3 of other group at a plurality o n s ng t e Fig 1 looking 1n the directi of t arrows; and length of the cylinder, and if appropriate pitch Fig 4 is an enlarged fragmentary View showing and spacing of the wires are used, the longitudinal an alternative grid sup orti means. 49 axes of the wires of one group will lie at an acute Mica spacers l a z, spaced fro each other angle to those of the other group at the crossover serve to support the tube element assembly a a P In Order t0 Produce a mechanically rigid whole between them and at the same time to 1n- Structure one which will be self'supporting sulate the e e t fro each othel These which will maintain its original shape whenthe spacers are of th conventmna] type and have 4 5 winding vform is removed, the wires are interprotuberances 3 at their outer edges WhlCh en- Woven interlaced with each Other- Wire 25 gage the inner walls of the tube envelop m t e of one group, for example, as shown in Fig. 2, usual way In order to maintain th spacer in inits helical progression around the cylinder,- fixed spatial relation rigid support rods 4 and 5 passes successively under and over the wires of extend between spacers I and 2, passing through 50 the other group; that is, it passes under wire 26, holes in the spacers. Clips 6 and 1 are firmly over wire 27, under wire 28, etc. The nextadattached to rods l and 5, respectively, for example jacent wire to Wire 5, in the same group, Which by welding, and bear on the upper surface of is wire 29,, passes successively over and under the spacer, I, as shown. Clips 8 and 9 are firmly atsame wires of the other group; that is, it passes tached to rods 4 and 5, respectively, in a similar over wire 26,, under wire 2 over wire 28, etc.

Wire 30, next adjacent to wire 29 in its group, duplicates the crossover-point positions of wire 25, and so on. The braiding or interweaving of the grid wires in this manner, due to the successive over-under-over crossings of each and every wire of one group with each and. every wire of the other group, results ina mechanically rigid grid structure, one which will maintain its original shape when it is mounted in the tube, without the use of any side supporting wires such as are required in the conventional grid or without its being necessary to fasten the individual wires to each other at points where they cross over each other. The interwoven grid structure may be mounted in the tube assembly by means engaging the structure only at its ends, as set forth in more detail hereinafter. Bythe interwoven grid structure of this invention, extremely close spacing of the wires, and therefore more effective control of the electron stream, may be had. Also, since no side support wires are needed, the hollow cylindrical grid can control the electron flow in the entire circular area around the filament.

It should be mentioned here that the Fig. '1 structure is shown greatly enlarged in the drawing, in order to make the details thereof easily discernible. Actually, of course, the tube element assembly is very much smaller in size than the showing of Fig. 1 might indicate, as this'invention has particular utility in extremely small tubes. The interwoven grid structure may be rapidly and conveniently produced, even though it is of such small dimensions, on an automatic braiding machine, and therefore may be made very inexpensively. 7

In order to bind the loose ends of the interwoven grid wires in place, and in order to form a mass for support of the grid and for convenient electrical connection thereto, the operating part of the grid is masked OE and molten metal is sprayed on the ends to form a metal band at each end which is solid and effectively integral with the grid itself. This effectively binds the wires to each other and prevents the whole from coming apart. The sprayed metal may be the same as that of the grid wires orit may be any other suitable type of metal, for example, nickel or copper. If it is either of the latter two metals, the spraying process may be used to make a cheap metal available as the band and some other desirable metal, for example tungsten, available as the-active portion'ofthe-grid; If desired, the band-'and-grid assembly can be fired after spraying to produce a better bond between the bands and the wires of the grid. Also, as an alternative procedure, prepared metallic bands can be welded to the braided structure instead of the spraying process being used.

In the drawing, l4 indicates the interwoven grid structure, and I5 indicates the metallic bands at both ends of the grid, said bands being applied either by spraying of the molten metal or by welding, as above described. Electrical connection to the grid may be easily made by spot welding lead Hi to the band l5 at the lower endof the grid, this lead passing through spacer 2 as shown.

In order to mount or supportthe grid between spacers I and 2, the mounting arrangement of Figs. 1-2 or that of Fig. 4 may be used. In Figs. 1 -2, ceramic disk H, which has a hole in its center through which element ll passes, fits inside grid I4 and firmly engages the interior surface of band 15 and also contacts the lower surface of spacer I. Ceramic collar l8 fits around and tightlyengages the outer surface of band l5 rigidly and is fastened to spacer l by any suitable fastening means I9. Bands l5, at each end of grid M, are in firm contact with the respective surfaces of spacers I and 2, and the lower end of grid 14 is mounted on spacer 2 in exactly the same manner as that described for the upper end of said grid and spacer I.

In Fig. 4, interwoven grid 14 is supported between spacers l and '2 by means of a pair of mica collars 2B which intimately engage the outer surface of the band l5, one at each end of the grid, and which are stapled at 21 to the corresponding mica spacers l and 2.

Anode or plate 22 surrounds grid l4, being on the opposite side of grid M from filament H, so that the grid is between the filament and the plate. Anode 22 is shown as being of cylindrical configuration, and is mounted between spacers l and 2 by means of integral tabs 22a which extend through the spacers and are fixed therein. Clip Lwhich is welded to rod 5 at one end, is spot welded at its other end to one of the tabs 2211, so that lead 23 may be electrically connected to the lower end of rod 5 to serve, by means of rod 5 and clip 1, as the plate lead of the tube.

The tube element assembly shown in Fig. l is in turn sealed in an envelope, not shown, in the conventional manner.

It is to be understood that this invention is not limited to the particular details as described above as many equivalents will suggest themselves to those skilled in the art. For example, although a tube with a single grid has been shown, it will be obvious that the invention is equally applicable to a multigrid tube, and in this event the mica collars or ceramic collars which mount or support the grid may also be utilized as spacing means between the separate grids. Although a tube with a single cylindrical anode has been illustrated, it is apparent that tubes with more than one anode, with a split anode, or with other anode shapes than that shown, may be used in the practice of the'invention. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of this invention within the art.

What is claimed is:

l. A grid element for a thermionic tube comprising a first group of individual wires progressing helically in one direction about the periphery of a cylinder, a second group of individual wires progressing helically in the oposite direction about said periphery, the two groups of wires being in interwoven relationship with each other at the points where they cross each other, and a solid metallic band rigidly fastened to each end of said element to prevent unraveling of the wires thereof.

2. A grid element for a thermionic tube comprising a first group of individual wires wound helically in one direction about the periphery of a cylinder, and a second group of individual wires wound helically in the opposite direction about said periphery, the longitudinal axes of the wires in the first group being parallel to each other and relatively close to each other, the longitudinal axes of the wires in the second group being parallel to each other, relatively close to each other, and at an acute angle to those of the first group, the wires of each group crossing those of the other group at acute angles at a plurality of points, each wire of either group passing over and under the successive wires of the other group at said points in its helical progression around the cylinder.

3. A grid element for a thermionic tube comprising a first group of individual wires wound helically in one direction about the periphery of a cylinder, and a second group of individual wires wound helically in the opposite direction about said periphery, the longitudinal axes of the wires in the second group being at an acute angle to those of the first group, the wires of each group crossing those of the other group at acute angles at a plurality of points, any wire of either group passing over and under the successive wires of the other group at said points in its helical progression around the cylinder, while the next adjacent wire to said last-mentioned wire passes under and over the same successive wires of the other group at corresponding points in its helical progression around the cylinder.

4. A thermionic tube structure comprising support means, an electron-emitting element, a grid surrounding said element, and at least one additional element surrounding said grid, said grid being made of a plurality of wires crossing each other at acute angles at a plurality of points and being interwoven with each other at the points of crossing, said grid having a metallic band integral with each end thereof, said grid being supported from said means by a disk of ceramic material inside the grid adjacent each end thereof which intimately engages the inner surface of each of the bands, and by a ring of ceramic material which surrounds and intimately engages each of said bands and is fastened to said means.

5. A thermionic tube structure comprising support means, an electron-emitting element, a grid surrounding said element, and at least one additional element surrounding said grid, said grid being made of a plurality of wires crossing each other at acute angles at a plurality of points and being interwoven with each other at the points of crossing, said grid having a metallic band integral with each end thereof, said grid being supported from said means by a collar of insulating material which surrounds and intimately engages each of said bands and is fastened to said means.

WILLIAM BRADFORD REED.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 225,754 Jenkins March 23, 1880 1,844,319 Hatt Feb. 9, 1932 1,963,254 Urmson June 19, 1934 2,002,667 Knoll May 28, 1935 FOREIGN PATENTS Number Country Date 4 9, 53 Gre t Br t in N v, 5 

